Pneumatic hammer

ABSTRACT

A hammer has a hood and means preventing the working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of the barrel and having a non-circular opening in the front end wall thereof, the hood embracing the lock so as to form an annular space therebetween. The front end wall of the hood is also provided with a non-circular opening and is rotatably mounted on the casing. The working tool is provided, at the first portion thereof adjacent to the shank, with a shoulder having a crosssection shape corresponding to the shape of the opening in the end wall of the lock, and the second portion of the working tool also has a non-circular cross-sectional shape corresponding to the shape of the opening in the end wall of the hood. The hood is operatively connected to the lock, and there are provided means for fixing the relative angular position of the hood and lock in the working position at which the openings in the end walls of the hood and lock are not in register, whereby the working tool is positively held in the lock.

United States Patent 1 Goppen et al.

[111 3,885,634 [451 May 27, 1975 PNEUMATIC HAMMER [76] Inventors: Albert Adolfovich Goppen, ulitsa Narodnogo opolchenia, 22, korpus 3, kv. 95; Igor Vladimirovich Nikolaev, ulitsa Fadeeva, 5, kv. 37,, both of Moscow; losif Fadeevich Vysotsky, Vladimirovsky pereulok, 5, kv. 44; Mikhail Maximovich Zaslavsky, Vladimirovsky pereulok, 4, kv. 4, both of Tomsk; Nikolai Alexandrovich Klushin, ulitsa Narodnaya 1, kv. 23; Anatoly Mikhailovich Petreev, ulitsa Sibiryakov-Gvardeitsev, 8, kv. 59, both of Novosibirsk; Lidia Mikhailovna Dronova, ulitsa Kalarash, 5, kv. 68, Ljubertsy Moskovskoi; Anatoly lvanovich Lednikov, Korovinskoe shosse 9, korpus 2, kv. 51; Jury Alexandrovich Grishenkov, Novye Cheremushki kvartal 34a, korpus l, kv. 73, both of Moscow; Jury Mikhailovich Bashlykov, ulitsa Kartasheva, 31B, kv. 18, Tomsk, all of USSR.

[22] Filed: May 23, 1974 [21] Appl. No.: 472,858

[52] US. Cl 173/104; 279/89 [51] Int. Cl B25d 9/00 [58] Field of Search 173/104; 279/9, 89, 1 B,

[56] References Cited UNITED STATES PATENTS Primary Examiner-James A. Leppink [5 7 ABSTRACT A hammer has a hood and means preventing the working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of the barrel and having a non-circular opening in the front end wall thereof, the hood embracing the lock so as to form an annular space therebetween. The front end wall of the hood is also provided with a non-circular opening and is rotatably mounted on the casing. The working tool is provided, at the first portion thereof adjacent to the shank, with a shoulder having a cross-section shape corresponding to the shape of the opening in the end wall of the lock, and the second portion of the working tool also has a non-circular cross-sectional shape corresponding to the shape of the opening in the end wall of the hood. The hood is operatively connected. to the lock, and there are provided means for fixing the relative angular position of the hood and lock in the working position at which the openings in the end walls of the hood and lock are not in register, whereby the working tool is positively held in the lock.

6 Claims, 14 Drawing Figures PM TED HAY 2 7 I975 SHEET PNEUMATIC HAMMER The invention relates to pneumatic hammers to be used in the machine building, construction and in the other industries.

Known in the art are pneumatic hammers comprising a casing accommodating a barrel axially movable relative to the casing, an air-distribution device and an impact mechanism with a hammer piston accommodated in the barrel and adapted to impart reciprocation to the hammer piston which imparts blows at the shank of a working tool mounted in the front portion of the barrel under the action of compressed air, a handle rigidly fixed to the casing, a guide bush fixed in the front portion of the barrel to receive the shank of the working tool, a hood mounted on the front portion of the hammer, and means preventing the working tool from falling out.

In this known construction of the hammer the working tool is prevented from falling out by means of balls located in a spring-loaded ring, and the working tool is provided with a groove to receive these balls.

In this prior art hammer, when a pressure is exerted on the working tool, the balls are disengaged from the tool so that, if the working tool gets sliding away from a workpiece, it may dart out from the hammer. When the hammer operates without a contact between the tool and a workpiece, the blows imparted at the shank of the working tool are transmitted to the hood, and the operators hands are subjected to an additional highlevel unhealthy vibration. In addition, the balls are free to move inside the ring along the circumference, whereby the rotation of the hood about its axis will not result in a corresponding rotation of the working tool so that this device can be employed only with the working tool having a non-circular shank.

Therefore, the known hammer has the following disadvantages.

The locking of the working tool in the hammer is unreliable so that the working tool may dart out from the hammer when the tool comes out of contact with a workpiece, or upon an accidental pressure on the starting lever, whereby the operator may be injured.

The construction of the hood does not provide for control of the working tool, that is for its rotation about the longitudinal axis of the hammer.

Furthermore, it should be noted that known pneumatic hammers do not ensure the fixing of the working tool at a predetermined angle with the concurrent provision of the positive locking of the working tool offering a guarantee against the shotting out of the tool.

The main object of the invention is to provide a pneumatic hammer ensuring a reliable and positive locking of the working tool in the hammer, 7

Another object of the invention is to provide a pneumatic hammer which allows convenient control of the working tool during the operation.

Still another object of the invention is to provide a pneumatic hammer which ensures a fixed positioning of the working tool at a predetermined angle.

Further object of the invention is to provide a pneumatic hammer having a lower vibration level in the zone of contact of the left hand of the operator with the hammer.

These and other objects are accomplished due to the fact that in a pneumatic hammer comprising a casing accommodating a barrel axially movable relative thereto, an air-distribution device and an impact mechanism with a hammer piston accommodated in the barrel and adapted to impart reciprocation to the hammer piston which imparts blows at the shank of a working tool mounted in the front portion of the barrel under the action of compressed air, a handle rigidly fixed to the casing, a guide bush fixed in the front portion of the barrel to receive the shank of the working tool, a hood mounted on the front portion of the hammer, and means preventing the working tool from falling out, in accordance with the invention, means preventing the working tool from falling out comprise a lock in the form of a tubular member, which has an end wall with a non-circular opening at its front end and is rotatably mounted on the front portion of the barrel, the hood also having an end wall with a non-circular opening at its front end and being rotatably mounted on the casing so as to embrace the lock in such a manner that an annular space is formed between the hood and the lock, the hood being operatively connected to the lock, while the working tool has one portion adjacent to the shank which is provided with a shoulder, the cross-sectional shape of the shoulder corresponding to the shape of the opening in the end wall of the lock, whereby, upon a relative angular rotation of the hood and lock, after the shoulder has been received in the lock opening, the working tool is held in the lock from falling out, and the other portion having a non-circular cross-sectional shape corresponding to the shape of the opening in the end wall of the hood so as to ensure an angular rotation of the working tool mounted in its operative position by rotating the hood, there being also provided means for locking the working tool in the hammer so as to fix the relative angular position of the hood and lock in the operative position in which the openings in the end walls of the hood and lock, respectively, are not in register, whereby the working tool is positively held in the lock.

This construction of the pneumatic hammer ensures a reliable positive locking of the working tool in the hammer, convenient control of the working tool during the operation, as well as the protection of the operators hand against unhealthy vibrations and injuries.

Means for locking the working tool in the hammer preferably comprise a ring having a pin with a leaf spring fixed thereto, the ring being rotatably mounted on the hood, and the hood having a through circular slot so that the pin extends through this slot, the lock preferably having a longitudinally extending slot to receive the pin end, the hood having an annular projection with a recess to receive the free end of said leaf spring, whereby the receive angular position of the hood and lock can be fixed.

With this construction of the pneumatic hammer there is provided convenient control of the working tool during the operation.

In accordance with another embodiment of the invention, means for locking the working tool in the hammer comprise a pin mounted in a radial hole of the lock, a circular slot and at least one longitudinally extending slot made in the hood and communicating therebetween, the hood being preferably axially springloaded relative to the casing so as to take the position at which the pin is received in the longitudinally extending slot, whereby the relative angular position of the hood and lock, at which the openings in the front I end walls thereof are not in register, can be fixed.

With this construction of the pneumatic hammer there is also ensured convenient control of the working tool.

When the lock is provided with one pin, the barrel is preferably provided with a radial hole coaxial with the radial hole of the lock, and the pin preferably has a shank received in the radial hole of the barrel.

This construction of the pneumatic hammer ensures the reliable prevention of the lock from being rotated relative to the barrel during the rotation of the hood to release the working tool from the lock and during the locking of the working tool in the lock by means of one and the same pin.

The barrel is preferably provided with a radial hole to receive a second pin, and the lock is provided with a second radial hole to receive the free end of this pin.

This construction of the pneumatic hammer also ensures the reliable prevention of the lock from rotating relative to the barrel during the rotation of the hood to release the working tool or during the locking of the working tool in the lock.

The lock is preferably provided with a circular slot, and the free end of the second pin is preferably received in this slot, the other end of the pin being received in the radial hole of the barrel.

This construction of the pneumatic hammer, while ensuring the control of the working tool during the operation, considerably increases the angle of rotation thereof which may be greater than 360 due to the presence of the circular slots both in the hood and lock so that one slot may constitute the extension of the other in the rotational direction.

The invention will now be described with reference to specific embodiments thereof illustrated in the accompanying drawings, in which:

FIG. 1 shows a longitudinal section of the pneumatic hammer according to the invention;

FIG. 2 is an enlarged sectional view taken along the line IIII in FIG. 1;

FIG. 3 is an enlarged sectional view taken along the line IIIIII in FIG. 1;

FIG. 4 is an enlarged sectional view taken along the line IV-IV in FIG. 1;

FIG. 5 is a view taken along the arrow A in FIG. 1;

FIG. 6 shows a longitudinal section of another embodiment of the pneumatic hammer according to the invention;

FIG. 7 is an enlarged detail B in FIG. 6;

FIG. 8 is a view taken along the arrow C in FIG. 6;

FIG. 9 is a sectional view taken along the line IXIX in FIG. 8;

FIG. 10 shows a longitudinal section of the front part of still another embodiment of the pneumatic hammer according to the invention (with two pins);

FIG. 11 is a sectional view taken along the line XI-XI in FIG. 10;

FIG. 12 is a sectional view taken along the line XII- XII in FIG. 10;

FIG. 13 shows a longitudinal section of the front part of a further embodiment of the pneumatic hammer according to the invention (with a pin having a shank);

FIG. 14 shows the section view taken along the line XI-XI in FIG. 10 with the pin received in the circular slot.

A pneumatic hammer comprises a casing 1 (FIGS. 1-15,12), a handle 2 rigidly fixed to the casing and having a triggering device to control the compressed air supply, as well as a passage for feeding compressed air (not shown), a starting lever 3 and a pipe connection 4 for connecting an air hose, as well as a barrel 5 mounted in the casing 1 and axially movable relative thereto. The casing 5 accommodates an impact mechanism and an air-distribution device (not shown) ensuring, under the action of compressed air, reciprocation of a hammer piston imparting blows at a shank 6a of a working tool 6. The triggering device, air-distribution device and impact mechanism may be of any appropriate design, they are well known to the persons skilled in the art and will not be described herein.

An annular space 7 is formed between the casing l and the barrel 5, and compressed air is admitted into this space through a passage from an air line and is then fed into the barrel 5. The barrel 5 has a portion 8 of a smaller diameter and a portion 9 of a greater diameter, and sealing bushes 10 and 11 are respectively mounted on these portions, a spring 12 disposed between the bushes urges the end faces of the bushes 10 and 11 against the casing 1. Therefore, a closed annular space is formed, wherein the compressed air pressure is permanently applied to a shoulder 13 formed between the portions 8,9 of the barrel having different diameter, the end face of the shoulder facing the handle 2.

The barrel 5 is externally provided with two annular rows a-a and bb of guide projections 14. Each row includes at least three projections 14, and the dimensions of the projections in the axial and circumferential direction are substantially smaller than the diameter of the contact surface between the projection 14 and the barrel 5. r

The above-described sealing and guiding means comprising sealing members 10,11 and guide members 14 are described in details in our co-pending application No. 472,864, filed May 23, 1974.

The working tool 6 is mounted in the front portion of the barrel 5, and the shank 6a thereof is received in a guide bush 15 which is fixed in the front portion of the 5 there is a lock 18 comprising a tubular member having at the front end thereof an end wall 19 with a noncircular opening 20. The hood 16 embraces the lock 18 in such a manner that an annular space 21 is formed therebetween, that is there is no direct contact between the hood 16 and the lock 18.

The hood 16 has an end wall 22 provided with a non-- circular opening 23.

The working tool 6 has a first portion 6b adjacent to the shank 6a which has a tapered shoulder 24 with flats 25, the cross-sectional shape of the tapered shoulder 24 corresponding to the shape of the opening 20 of the lock 18. The tapered shape of the shoulder improves its strength which is critical since both the shoulder 24 and the lock 18 receive idle blows of the hammer piston, while, the presence of the flats 25 on the shoulder 24 allows the passage of the shoulder 24 through the opening 20 in the lock 18. In the position shown in FIGS. 1 and 3 the lock 18 is rotated relative to the working tool 6 so that the working tool 6 is positively held in the lock The working tool 6 has a second portion 60 having the cross-sectional shape corresponding to the shape of the opening 23 in the end wall 22 of the hood 16, whereby a rotation of the hood 16 will result in rotation of the working tool 6.

The hood 16 is provided with a ring 26 (FIGS. 1,4 and 5) which is rotatably mounted thereon. A pin 27 is fixed to the ring 26 and extends in a through circular slot 28 (FIG. 4) of the hood 16. The end of the pin 27 is received in a longitudinally extending slot 29 (FIGS. 1,4) of the lock 18 in such a manner that, upon a rotation of the ring 26, the lock 18 will be rotated about the longitudinal axis of the hammer, whereby the working tool 6 can be locked in the lock 18 or released therefrom.

In order to fix the ring 26, and hence the lock 18, in

the operative position, at which the working tool is.

locked in the hammer, there is provided a leaf spring 30 (FIG. 1) which is fixed to the pin 27. The hood 16 is externally provided with an annular projection 31 (FIGS. 1,5) having a recess 32 to receive the end of the spring 30, whereby the operative position of the lock 18 can be fixed.

In order to reduce the unhealthy effect of vibration on the operators hand, the hood 16 is provided with an elastic liner 33 (FIGS. 1, l,6,7,l1)

The above-described embodiment of the hammer may be employed with a working tool having a round shank, and yet it will allow the control of the working tool during the operation.

The following description of other embodiments of the hammer according to the present invention relates to the constructions which allow the employment of a working tool having any cross-sectional shape of the shank; in addition they ensure a fixed positioning of the working tool at a predetermined angle, even if it has a round shank.

Referring to the other embodiments of the invention illustrated in FIGS. 6 14, wherein the identical parts are indicated with the same reference numerals as in FIGS. 1-5, a pneumatic hammer shown in FIGS. 6,7,8 and 9 has the hood l6 rotatably mounted on the casing l and the lock 18 rotatably mounted on the barrel 5. A pin 34 is mounted in a radial hole 35 of the lock 18 and extends through a longitudinally extending slot 36 of the hood 16. The hood 16 has a circular slot 37 communicated with the longitudinally extending slot 36. The hood 16 is axially movable relative to the casing l and is axially spring-loaded by means of a spring 38 (FIG. 6). With this embodiment, when the pressure is exerted on the hood 16 in the direction toward the handle 2, the pin 34 is received in the circular slot 37, whereafter the hood 16 can be rotated so as to rotate the working tool 6 due to its cooperation with the walls of the non-circular opening 23 of the hood 16, whereby the openings 23 and 20 of the hood and lock, respectively, may be brought in register.

With this embodiment the stepless control of the position of the working tool 6 is ensured. In order to position the working tool 6 at a predetermined fixed angle, the lock 18 should be prevented from rotating on the barrel 5.

Accordingly, a second pin 40 is mounted in a radial hole 39 of the barrel 5 (FIGS. 10,11) the pin being received in a radial hole 41 of the lock 18. With such a construction the working tool 6 can be fixed in the pneumatic hammer at a predetermined angle.

The pin 34 can also perform the function of the second pin 40, and for that purpose the pin 34 is provided with a shank 34a (FIG. 13) which is received in a radial hole 42 of the barrel 5.

In another embodiment of the invention, the hood 16 (FIG. 10) has the circular slot 37 and at least two longitudinally extening slots 36 and 43 communicated therewith. The pin 34 may be received in one of said slots by pressing the hood 16 and rotating it about the longitudinal axis of the hammer. When the pin 34 is received in the slot 36 or 43, the hood 16 positions the working tool 6 into the operative position in which the latter is held in the lock 18 at different fixed angles. When the pin 34 is received in a portion 37a of the circular slot 37, the opening 23 of the hood 16 is in register with the opening 20 of the lock 18 so that the working tool may be withdrawn from the hammer.

In order to allow the stepless rotation of the working tool 6 at any desired angle during the operation, the lock 18 is provided with a circular slot 44 (FIG. 14) in which the second pin 40 is receiver; for that purpose the pin 40 is withdrawn from the hole 41 (FIG. 11) of the lock 18 and is inserted into the slot 44 (FIG. 14). With this embodiment, the pin 34 may be received in any of the longitudinal slots 36, 43 so that a rotation of the hood 16 will result in rotation of the working tool 6 about the longitudinal axis of the hammer, the tool remaining locked in the lock 18.

The pneumatic hammer shown in FIGS. 1-5 functions as follows.

Prior to the beginning of the operation, the operator disengages the leaf spring 30 from the recess 32 and rotates the ring 26 so as to rotate the lock 18 until the openings 20 and 23 are brought in register. Then the operator inserts the working tool 6 into the hammer through the openings 23 and 20 so that the shank 6a should be received in the guide bush 15. The ring 26 is subsequently rotated in the opposite direction until the leaf spring 30 is received in the recess 32. In this position the working tool 6 is locked in the lock 18. The

withdrawn of the working tool 6 from the hammer is made in the reversed order. The hammer is then positioned so that the working tool 6 should bear against a workpiece (not shown), and then, by exerting a pressure on the starting lever 3, compressed air is admitted into the annular space (space 7), wherefrom the compressed air is fed into the barrel 5.

During the operation, the operator holds the hammer with one hand gripping the handle 2 and with the other hand gripping the hood 16. By rotating the hood 16, the operator can position the working tool 6 at any angle convenient for a given application.

Since the lock 18 is operatively connected to the hood 16 by means of the pin 27, a rotation of the hood 16 together with the working tool 6 will result in rotation of the lock 18, whereby the working tool 6 is permanently positively held in the hammer.

It should be noted that, due to the absence of any direct contact between the hood 16 and the barrel 5, as well as due to the employment of the elastic liner 33 on the hood 16, vibration generated in this zone of the hammer will not have any unhealthy effect on the operator.

The pneumatic hammer shown inYFIGS. 6-14 functions as follows.

Prior to the beginning of the operation, the operator urges the hood 16 towards the handle 2 to compress the spring 38, and while rotating the hood 16, brings it into a position such that the pin 34 should be in the portion 37a of the circular slot 37 of the hood 16. In this position the openings 23 and 20 of the hood l6 and lock 18 are in register. Then the operator inserts the working tool 6 into the hammer through the openings 23 and 20 so that the shank 6a should be received in the guide bush 15. Subsequently the operator rotates the hood to position the pin 34 opposite one of the longitudinally extending slots 36,43 so that the pin can enter this slot under the action of the spring 38. After that the working tool 6 is locked in the lock 18. Further operation of the pneumatic tool is identical with the abovedescribed operation of the hammer with reference to FIGS. l-S.

The working tool is withdrawn in the reversed order.

Depending on desired production technique one of the embodiments of the invention described with reference to FIGS. 6-14 may be selected.

When it is necessary to ensure the stepless control of the working tool 6 over a limited angular range, the hammer shown in FIGS. 6, 6,7,8,9,12 will be selected, wherein the pin 34 is received in the radial hole. 35 of the lock 18 and extends through the longitudinally extending slot 36 of the hood 16.

In that case the operator rotates the hood 16 to insert the working tool 6 and locks it in the hammer as it was described above. Then the operator rotates the hood 16 to position the working'tool 7 within the limits of the rotational angle of the lock 18. Since the lock 18 is operatively connected to the hood 16 by means of the pin 34, a rotation of the hood 16 together with the working tool 6 will result in rotation of the lock 18, whereby the working tool 6 will be permanently positively held in the hammer.

When it is desired to fix the working tool 6 at a preselected angle, the hammers shown in FIGS. 8,10,11,13 are used. In one case, (FIGS. 8,10,11), the second pin 40 is inserted into the radial hole 39 of the barrel 5, the free end of the pin 40 being received in the radial hole 41 of the lock 18. In another case (FIGS. 8,13) the pin 34 has the shank 34a which is inserted into the radial hole 42 of the barrel, and the hood 16 has one longitudinal slot 36. In these cases the operator rotates the hood 16 to insert the working tool 6 into the hammer, and locks it as it was described above.

Then the operator positions the working tool 6 at one preselected angle. Since the lock 18 is connected to the barrel by means of the second pin 40 or by means of the shank 34a of the pin 34, and is operatively connected to the hood 16 by means of the pin 34, the rotation of the hood 16, which is connected to the working tool 6 locked in the lock 18, is not possible, and the angle determiningthe position of the working tool 6 with respect to a workpiece (not shown) depends on the relative angular position of the longitudinally extending slot 36 of the hood 16 and the opening 23 in the end wall 22 of the hood 16.

When it is desired to provide the stepless control of the working tool 6 without limiting its rotational angle, the hammer shown in FIGS. 8,14 is employed, wherein the lock 18 has the circular slot 44 in which there is received the second pin 40 mounted in the barrel 5. Thus, the operator rotates the hood 16 to insert the working tool 6 into the hammer, and locks the working tool as it was described above. Subsequently the operator rotates the hood 16 to rotate the working tool first through the angle of rotation of the lock 18 relative to the barrel 5, and then, continuing the rotation of the hood 16, he can additionally rotate the working tool 6 through the angular length of the circular slot 44 so that a total angle of rotation of the working tool may exceed 360.

Where it is desired to fix the working tool 6 at different angles, the hammer shown in FIG. 8. is employed, wherein the hood 16 has two longitudinally extending slots 36 and 43 (a plurality of such slots may be provided). Thus, the operator rotates the hood 16 to insert the working tool 6, and locks it in the hammer as it was described above. Then, in order to change the angle of inclination of the working tool 6 with respect to a workpiece, (not shown), the operator urges the hood 16 towards the handle 2 to disengage the pin 34 from the longitudinally extending slot 36 and to place it into the circular slot 37, and subsequently rotates the hood 16 to position the pin 34 opposite the longitudinally extending slot 43 so that is should enter this slot under the action of the spring 38.

It should be noted that in all cases, during the rotation of the hood 16, the hence, of the working tool 6, the lock 18, which is operatively connected to the hood 16 by means of the pin 34, will be also caused to rotate,

whereby the working tool 6 is positively held in the hammer.

It will be apparent from the above description that the pneumatic hammer according to the invention ensures a reliable positive locking of the working tool,

convenient control of the working tool during the operation and the protection of the operator against the unhealthy effect of vibration and injuries.

The above-described embodiments of the pneumatic hammer was given as illustrative examples only which by no means limit the scope of the invention. Various modifications may be introduced by the persons skilled in the art without the departure from the spirit and scope of the invention defined by the appended claims.

The commercial tests of the pneumatic hammer constructed in accordance with the present invention have shown that the hammer ensures a reliable locking of the working tool, convenient control thereof during the operation and lower vibration level at the hood which is below the admissible level.

What is claimed is:

1. A pneumatic hammer comprising: a casing; a barrel in said casing, said barrel being axially movable relative to said casing; a working tool mounted in the front portion of said barrel, said working tool having a shank; an air-distribution device and an impact mechanism with a hammer piston in said barrel, said airdistribution device and impact mechanism ensuring reciprocation of said hammer piston imparting blows at the shank of said working tool under the action of compressed air; a guide bush fixed in the front portion of said barrel, the shank of said working tool being received in said guide bush; a hood mounted on the front portion of the hammer; means preventing said working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of said barrel; an end wall at the front end of said lock, said end wall having an non-circular opening; said hood being rotatably mounted on said casing and embracing said lock so as to form an annular space therebetween; an end wall at the front end of said hood, said end wall having a non-circular opening; a first portion of said working tool adjacent to the shank thereof, said first portion having a shoulder, the cross-sectional shape of said shoulder corresponding to the shape of the opening of said end wall of said lock, whereby, upon a relative angular rotation of said hood and lock, after said shoulder has been received in the opening of said lock, said working tool is held-in said lock from falling out; a second portion of said working tool having a non-circular cross-sectional shape corresponding to the shape of the opening of said end wall of said hood so as to ensure an angular rotation of said working tool when in the operative position by rotating said hood; means for locking said working tool in the hammer, said means providing the fixing of the relative angular position of said hood and lock in the operative position at which the openings of said end walls of said hood and lock are not in register, whereby said working tool is positively held in said lock.

2. A pneumatic hammer comprising: a casing; a barrel in said casing, said barrel being axially movable relative to said casing; a working tool mounted in the front portion of said barrel, said working tool having a shank; an air-distribution device and an impact mechanism with a hammer piston in said barrel, said airdistribution device and impact mechanism ensuring reciprocation of said hammer piston imparting blows at the shank of said working tool under the action of compressed air; a guide bush fixed in the front portion of said barrel, the shank of said working tool being received in said guide bush; a hood mounted on the front portion of the hammer; means preventing said working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of said barrel; an end wall at the front end of said lock, said end wall having a non-circular opening; said hood being rotatably mounted on said casing and embracing said lock so as to form an annular space therebetween; an end wall at the front end of said hood, said end wall having a non-circular opening; a first portion of said working tool adjacent to the shank thereof, said first portion having a shoulder, the cross-sectional shape of said shoulder corresponding to the shape of the opening of said end wall of said lock, whereby, upon a relative angular rotation of said hood and lock, after said shoulder has been received in the opening of said lock, said working tool is held in said lock from falling out; a second portion of said working tool having a non-circular cross-sectional shape corresponding to the shape of the opening of said end wall of said hood so as to ensure an angular rotation of said working tool when in the operative position by rotating said hood; means for locking said working too] in the hammer, said means providing the fixing of the relative angular position of said hood and lock in the operative position at which the openings of said end walls of said hood and lock are not in register, whereby said working tool is positively held in said lock, said means for locking said working tool in the hammer comprising: a ring rotatably mounted on said hood, a pin fixed to said ring, said hood having a circular slot and said pin extending through said slot, said lock having a longitudinally extending slot to receive said pin, a leaf spring being fixed to said pin for fixing the relative angular position of said hood and lock, and said hood being externally provided with a projection having a recess in which the free end of said leaf spring is received.

3. A pneumatic hammer comprising: a casing; a barrel in said casing, said barrel being axially movable relative to said casing; a working tool mounted in the front portion of said barrel, said working tool having a shank; an air-distribution device and an impact mechanism with a hammer piston in said barrel, said airdistribution device and impact mechanism ensuring reciprocation of said hammer piston imparting blows at the shank of said working tool under the action of compressed air; a guide bush fixed in the front portion of said barrel, the shank of said working tool being received in said guide bush; a hood mounted on the front portion of the hammer; means preventing said working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of said barrel; an end wall at the front end of said lock, said end wall having a none-circular opening; said hood being rotatably mounted on said casing and embracing said lock so as to form an annular space therebetween; an end wall at the front end of said hood, said end wall having a non-circular opening; a first portion of said working tool adjacent to the shank thereof, said first portion having a shoulder, the cross-sectional shape of said shoulder corresponding, to the shape of the opening of said end wall of said lock, whereby, upon a relative angular rotation of said hood and said lock, after said shoulder has been received in the opening of said lock, said working tool is held in said lock from falling out; a second portion of said working tool having a non-circular cross-sectional shape corresponding to the shape of the opening of said end wall of said hood so as to ensure an angular rotation of said working tool when in the operative position by rotating said hood; means for locking said working tool in the hammer, said means comprising said lock having a ra- I dial hole, a pin mounted in said radial hole of said lock, said hood having a circular slot and at least one longitudinally extending slot communicated with said circular slot, said hood being axially spring-loaded relative to said casing so as to take the position at which said pin is received in said longitudinally extending slot for fixing the relative angular position of said hood and lock' in which said openings of said end walls thereof are not in register, whereby said working tool is positively held in said lock.

4. A pneumatic hammer according to claim 3, wherein said barrel has a radial hold coaxial with said radial hole of said lock, and said pin is provided with a shank receiver in said radial hole of the barrel.

5. A pneumatic hammer according to claim 3, wherein said barrel has a radial hole, said lock has a second radial hole, and there is provided a second pin having one end mounted in said radial hole of the barrel, the free end of the pin being received in said radial hole of said lock.

6. A pneumatic hammer comprising: a casing; a barrel in said casing, said barrel being axially movable relative to said casing; a working tool mounted in the front portion of said barrel, said working tool having a shank;

- an air-distribution device and an impact mechanism portion of the hammer; means preventing said working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of said barrel; an end wall at the front end of said lock; said end wall having a non-circular opening; said hood being rotatably mounted on said casing and embracing said lock so as to form an annular space therebetween; an end wall at the front end of said hood, said end wall having a non-circular opening; a first portion of said working tool adjacent to the shank thereof, said first portion having a shoulder, the cross-sectional shape of said shoulder corresponding to the shape of the opening of said end wall of said lock, whereby, upon a relative angular rotation of said hood and said lock, after said shoulder has been received in the opening of said lock, said working tool is held in said lock from falling out; a second portion of said working tool having a non-circular cross-sectional shape corresponding to the shape of the opening of said end wall of said hood so as to ensure an angular rotation of said working tool when in the operative position by rotating said hood; means for locking said working tool in the hammer, said means comprising said lock having a radial hole, a pin mounted in said hole of said lock, said hood having a circular slot and at least one longitudinal slot communicated with said circular slot, said hood being axially spring-loaded relative to said casing so as to take the position at which said pin is received in said longitudinally extending slot for fixing the relative angular position of said hood and lock at which the openings in said end walls thereof are not in register, whereby said working tool is positively held in said lock, said barrel having a radial hole, a second pin being mounted in said radial hole of the barrel, said lock having a circular slot and said second pin having the free end movably received in said circular slot. 

1. A pneumatic hammer comprising: a casing; a barrel in said casing, said barrel being axially movable relative to said casing; a working tool mounted in the front portion of said barrel, said working tool having a shank; an air-distribution device and an impact mechanism with a hammer piston in said barrel, said air-distribution device and impact mechanism ensuring reciprocation of said hammer piston imparting blows at the shank of said working tool under the action of compressed air; a guide bush fixed in the front portion of said barrel, the shank of said working tool being received in said guide bush; a hood mounted on the front portion of the hammer; means preventing said working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of said barrel; an end wall at the front end of said lock, said end wall having an non-circular opening; said hood being rotatably mounted on said casing and embracing said lock so as to form an annular space therebetween; an end wall at the front end of said hood, said end wall having a non-circular opening; a first portion of said working tool adjacent to the shank thereof, said first portion having a shoulder, the crosssectional shape of said shoulder corresponding to the shape of the opening of said end wall of said lock, whereby, upon a relative angular rotation of said hood and lock, after said shoulder has been received in the opening of said lock, said working tool is held in said lock from falling out; a second portion of said working tool having a non-circular crosssectional shape corresponding to the shape of the opening of said end wall of said hood so as to ensure an angular rotation of said working tool when in the operative position by rotating said hood; means for locking said working tool in the hammer, said means providing the fixing of the relative angular position of said hood and lock in the operative position at which the openings of said end walls of said hood and lock are not in register, whereby said working tool is positively held in said lock.
 2. A pneumatic hammer comprising: a casing; a barrel in said casing, said barrel being axially movable relative to said casing; a working tool mounted in the front portion of said barrel, said working tool having a shank; an air-distribution device and an impact mechanism with a hammer piston in said barrel, said air-distribution device and impact mechanism ensuring reciprocation of said hammer piston imparting blows at the shank of said working tool under the action of compressed air; a guide bush fixed in the front portion of said barrel, the shank of said working tool being received in said guide bush; a hood mounted on the front portion of the hammer; means preventing said working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of said barrel; an end wall at the front end of said lock, said end wall having a non-circular opening; said hood being rotatably mounted on said casing and embracing said lock so as to form an annular space therebetween; an end wall at the front end of said hood, said end wall having a non-circular opening; a first portion of said working tool adjacent to the shank thereof, said first portion having a shoulder, the cross-sectional shape of said shoulder corresponding to the shape of the opening of said end wall of said lock, whereby, upon a relative angular rotation of said hood and lock, after said shoulder has been reCeived in the opening of said lock, said working tool is held in said lock from falling out; a second portion of said working tool having a non-circular cross-sectional shape corresponding to the shape of the opening of said end wall of said hood so as to ensure an angular rotation of said working tool when in the operative position by rotating said hood; means for locking said working tool in the hammer, said means providing the fixing of the relative angular position of said hood and lock in the operative position at which the openings of said end walls of said hood and lock are not in register, whereby said working tool is positively held in said lock, said means for locking said working tool in the hammer comprising: a ring rotatably mounted on said hood, a pin fixed to said ring, said hood having a circular slot and said pin extending through said slot, said lock having a longitudinally extending slot to receive said pin, a leaf spring being fixed to said pin for fixing the relative angular position of said hood and lock, and said hood being externally provided with a projection having a recess in which the free end of said leaf spring is received.
 3. A pneumatic hammer comprising: a casing; a barrel in said casing, said barrel being axially movable relative to said casing; a working tool mounted in the front portion of said barrel, said working tool having a shank; an air-distribution device and an impact mechanism with a hammer piston in said barrel, said air-distribution device and impact mechanism ensuring reciprocation of said hammer piston imparting blows at the shank of said working tool under the action of compressed air; a guide bush fixed in the front portion of said barrel, the shank of said working tool being received in said guide bush; a hood mounted on the front portion of the hammer; means preventing said working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of said barrel; an end wall at the front end of said lock, said end wall having a none-circular opening; said hood being rotatably mounted on said casing and embracing said lock so as to form an annular space therebetween; an end wall at the front end of said hood, said end wall having a non-circular opening; a first portion of said working tool adjacent to the shank thereof, said first portion having a shoulder, the cross-sectional shape of said shoulder corresponding, to the shape of the opening of said end wall of said lock, whereby, upon a relative angular rotation of said hood and said lock, after said shoulder has been received in the opening of said lock, said working tool is held in said lock from falling out; a second portion of said working tool having a non-circular cross-sectional shape corresponding to the shape of the opening of said end wall of said hood so as to ensure an angular rotation of said working tool when in the operative position by rotating said hood; means for locking said working tool in the hammer, said means comprising said lock having a radial hole, a pin mounted in said radial hole of said lock, said hood having a circular slot and at least one longitudinally extending slot communicated with said circular slot, said hood being axially spring-loaded relative to said casing so as to take the position at which said pin is received in said longitudinally extending slot for fixing the relative angular position of said hood and lock in which said openings of said end walls thereof are not in register, whereby said working tool is positively held in said lock.
 4. A pneumatic hammer according to claim 3, wherein said barrel has a radial hold coaxial with said radial hole of said lock, and said pin is provided with a shank receiver in said radial hole of the barrel.
 5. A pneumatic hammer according to claim 3, wherein said barrel has a radial hole, said lock has a second radial hole, and there is provided a second pin having one end mounted in said radial hole of the barrel, the free end of the pin bEing received in said radial hole of said lock.
 6. A pneumatic hammer comprising: a casing; a barrel in said casing, said barrel being axially movable relative to said casing; a working tool mounted in the front portion of said barrel, said working tool having a shank; an air-distribution device and an impact mechanism with a hammer piston in said barrel, said aid-distribution device and impact mechanism ensuring reciprocation of said hammer piston imparting blows at the shank of said working tool under the action of compressed air; a guide bush fixed in the front portion of said barrel, the shank of said working tool being received in said guide bush; a hood mounted on the front portion of the hammer; means preventing said working tool from falling out, said means comprising a lock in the form of a tubular member rotatably mounted on the front portion of said barrel; an end wall at the front end of said lock; said end wall having a non-circular opening; said hood being rotatably mounted on said casing and embracing said lock so as to form an annular space therebetween; an end wall at the front end of said hood, said end wall having a non-circular opening; a first portion of said working tool adjacent to the shank thereof, said first portion having a shoulder, the cross-sectional shape of said shoulder corresponding to the shape of the opening of said end wall of said lock, whereby, upon a relative angular rotation of said hood and said lock, after said shoulder has been received in the opening of said lock, said working tool is held in said lock from falling out; a second portion of said working tool having a non-circular cross-sectional shape corresponding to the shape of the opening of said end wall of said hood so as to ensure an angular rotation of said working tool when in the operative position by rotating said hood; means for locking said working tool in the hammer, said means comprising said lock having a radial hole, a pin mounted in said hole of said lock, said hood having a circular slot and at least one longitudinal slot communicated with said circular slot, said hood being axially spring-loaded relative to said casing so as to take the position at which said pin is received in said longitudinally extending slot for fixing the relative angular position of said hood and lock at which the openings in said end walls thereof are not in register, whereby said working tool is positively held in said lock, said barrel having a radial hole, a second pin being mounted in said radial hole of the barrel, said lock having a circular slot and said second pin having the free end movably received in said circular slot. 